This invention relates to semiconductor integrated circuit structures. More particularly, it is concerned with substrates for the fabrication of semiconductor integrated circuit devices therein and with methods of producing such substrates.
Monolithic semiconductor integrated circuit structures, or chips, which employ bipolar and MOS type devices are well-known and widely used. Typically the devices are of low voltage and low power. Electrical connections to the devices are at the upper surface of the chip or in the semiconductor material adjacent to the upper surface.
For many applications it is desirable to employ relatively high voltage, high power devices and low voltage, low power devices within the same chip. Typically, high voltage, high power devices are of vertical configuration; that is, current flow in the device is vertical between the upper surface and the lower surface of the chip rather than lateral. Although the processing steps employed in the fabrication of these devices may be compatible with those employed in the fabrication of low voltage, low power MOS and bipolar devices, techniques typically employed to provide electrical isolation between the individual devices in a chip do not permit more than one device of vertical structure within a chip.